Immobilized cells are effective catalysts in the enzymatic conversion of organic ingredients. It is known to effect the immobilization of cells by introducing the cells together with a supporting substance into a polymer solution which is capable of gelling and then runs out with formation of drops from the immobilization vessel and falls into a collecting vessel which contains a solution of a cross-linking agent (J. Klein and K.-D. Vorlop (1983) ACS Symposium Series 207, 377-392; American Chemical Society, 1983, 17). The drops are formed by supplying sterile compressed air coaxially to the discharge pipes coming out of hte immobilization vessel, said compressed air sweeping along the discharge pipes and facilitating the shaping and detachment of the discharge pipe. While freely falling down and being cross linked, the drops assume the shape of balls or beads so that biocatalyst beads in the form of balls are present in the collecting vessel.
It is of particular importance when immobilizing cells to maintain them sterile before and during the immobilization process. When using the known apparatus, it is necessary to separately pre-sterilize all of the parts and thereafter use them in a sterile atmosphere.